This invention relates in general to vehicle drive train assemblies for transferring rotational power, such as from an engine to an axle assembly of the vehicle. In particular, this invention relates to a drive train member such as a driveshaft having convex splines.
In most land vehicles in use today, a drive train assembly is provided for transmitting rotational power from an engine/transmission assembly to one or more wheels of the vehicle. In a rear-wheel drive vehicle, a typical drive train assembly includes a tubular driveshaft which is connected between an output shaft of the transmission and an input shaft of a rear axle assembly to rotatably drive the rear wheels. In a front-wheel drive vehicle, a typical drive train assembly includes right and left halfshafts which are connected between a transaxle assembly and the right and left wheels, respectively.
In a four-wheel drive vehicle, such as shown in FIG. 10, a typical drive train assembly includes a transfer case which rotatably supports an input shaft for receiving rotational power from the engine/transmission assembly, as well as front and rear output shafts for transferring rotational power from the input shaft to the front and rear wheels of the vehicle, respectively. Typically, a front auxiliary driveshaft is connected between the front output shaft of the transfer case and an input shaft of a front axle assembly to rotatably drive the front wheels, and a rear driveshaft is connected between the rear output shaft of the transfer case and an input shaft of the rear axle assembly to rotatably drive the rear wheels. In some vehicles, the transfer case is spaced apart from the transmission, and a front driveshaft is connected between the output shaft of the transmission and the input shaft of the transfer case.
The different shafts are usually connected together by the use of universal joints. For example, a first universal joint is usually connected between the front output shaft of the transfer case and a first end of the front auxiliary driveshaft, and a second universal joint is connected between a second end of the front auxiliary driveshaft and the input shaft of the front axle assembly. The universal joints provide a rotational driving connection from the front output shaft of the transfer case through the front auxiliary driveshaft to the input shaft of the front axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts. The use of universal joints to connect both ends of a driveshaft increases the complexity and cost of the drive train assembly.